Structure and method for replacement gate MOSFET with self-aligned contact using sacrificial mandrel dielectric

Abstract

The present disclosure provides a method for forming a semiconductor device that includes forming a replacement gate structure overlying a channel region of a substrate. A mandrel dielectric layer is formed overlying source and drain regions of the substrate. The replacement gate structure is removed to provide an opening exposing the channel region of the substrate. A functional gate structure is formed over the channel region including a work function metal layer. A protective cap structure is formed over the functional gate structure. At least one via is etched through the mandrel dielectric layer selective to the protective cap structure to expose a portion of at least one of the source region and the drain region. A conductive fill is then formed in the vias to provide a contact to the at least one of the source region and the drain region.

What is claimed is: 
     
       1. A method of forming a semiconductor device comprising:
 forming a protective dielectric layer on sidewalls of a replacement gate structure that is present over a channel region of a substrate; 
 forming a source region and a drain region on opposing sides of the replacement gate structure; 
 forming a mandrel dielectric layer overlying the source region and the drain region of the substrate, wherein the mandrel dielectric layer has an upper surface that is coplanar with an upper surface of the replacement gate structure; 
 removing the replacement gate structure to provide an opening exposing the channel region of the substrate; 
 forming a gate dielectric layer over the channel region and sidewalls of the opening; 
 forming a work function metal layer on the gate dielectric layer; 
 forming a metal fill material on the work function metal layer; 
 recessing the metal fill material, said recessing forming a surface dielectric layer on a recessed surface of a remaining portion of the metal fill material, wherein an upper surface of the surface dielectric layer is below the upper surface of the mandrel dielectric layer; 
 recessing vertical portions of the work function metal layer to form a U-shaped work function metal layer, wherein upper surfaces of the U-shaped work function metal layer are coplanar with or below the upper surface of the surface dielectric layer; 
 forming a protective dielectric cap structure over the upper surface of the surface dielectric layer and the upper surfaces of the U-shaped work function metal layer; 
 etching at least one via through the mandrel dielectric layer selective to the protective dielectric cap structure and the protective dielectric layer to expose a portion of at least one of the source region and the drain region; and 
 forming a conductive fill in at least one via to provide a contact to the at least one of the source region and the drain region. 
 
     
     
       2. The method of  claim 1  further comprising removing the mandrel dielectric layer, and forming a stress-inducing layer overlying the functional gate structure. 
     
     
       3. The method of  claim 2 , wherein the stress-inducing layer induces a compressive or tensile stress on the channel region of the substrate. 
     
     
       4. The method of  claim 1  wherein forming the replacement gate structure overlying the channel region of the substrate comprises:
 providing a substrate; 
 depositing a sacrificial layer on the substrate; and 
 patterning the sacrificial layer to provide the replacement gate structure. 
 
     
     
       5. The method of  claim 4 , wherein the sacrificial layer comprises a dielectric layer; and pattering the sacrificial layer comprises forming photoresist mask overlying the dielectric layer and etching the dielectric layer selective to the photoresist mask and the substrate. 
     
     
       6. The method of  claim 4 , wherein the forming of the mandrel dielectric layer comprises depositing a dielectric layer having a composition to be etched selective to the protective dielectric layer and the protective dielectric cap, and planarizing the mandrel dielectric layer until an upper surface of the replacement gate structure is exposed. 
     
     
       7. The method of  claim 1 , wherein the forming of the source region and the drain region on opposing sides of the replacement gate structure comprises ion implantation to form n-type or p-type dopant regions into the substrate, and forming a metal semiconductor alloy material on the n-type or p-type dopant regions. 
     
     
       8. The method of  claim 1 , wherein the removing of the replacement gate structure to provide the opening exposing the channel region of the substrate comprises etching the replacement gate structure selective to the mandrel dielectric layer and the substrate. 
     
     
       9. The method of  claim 1 , wherein the forming of the gate dielectric layer comprises a conformal deposition of high-k dielectric material. 
     
     
       10. The method of  claim 1 , wherein the forming of the metal work function layer comprises a conformal deposition of a metal layer that effectuates an n-type threshold voltage shift or a metal layer that effectuates a p-type threshold voltage shift, wherein the metal work function layer is present on the portion of the high-k dielectric layer that is present on the channel region and is present on the portion of the high-k dielectric that is present on the sidewalls of the opening. 
     
     
       11. The method of  claim 1 , wherein the forming of the metal fill material on the work function metal layer comprises filling the opening with the metal fill material. 
     
     
       12. The method of  claim 1 , wherein after the recessing of the vertical portions of the metal work function layer that is present on the high-k dielectric layer that is present on the sidewalls of the opening, a remaining portion of the metal work function layer remains in a lower portion of the opening. 
     
     
       13. The method of  claim 1 , wherein the forming of the protective dielectric cap structure over the upper surface of the surface dielectric layer and the upper surfaces of the U-shaped work function metal layer comprises depositing a dielectric material to fill the upper portion of the opening. 
     
     
       14. The method of  claim 1 , wherein the etching at least one via through the mandrel dielectric layer selective to the protective cap structure and the protective dielectric layer comprises an anisotropic etch process.